The invention concerns a process for the production of isobutene and propylene from a C.sub.4 cut.
Steam cracking feeds constituted by light paraffinic cuts produces ethylene and propylene which are required for petrochemistry. It also produces a certain number of other heavier products, in particular a C.sub.4 hydrocarbon cut which principally contains 1,3-butadiene, isobutene, n-butenes and butanes, accompanied by traces of acetylenic hydrocarbons.
In addition to gasoline and gas oil as the principal products, catalytic cracking of heavy hydrocarbon feeds produces lighter products, among them a C.sub.4 hydrocarbon cut which contains principally isobutane, isobutene, n-butenes and butanes, accompanied by small quantities of 1,3-butadiene and acetylenic hydrocarbons.
Until recently, only 1,3-butadiene and isobutene were of use in the polymer industry, in particular the tire industry for the former. An increase in the longevity of tires and a relative stagnation in demand have meant that there is now a surplus of butadiene which is not used or is not used properly. In contrast, there has been a reawakening in interest in isobutene which can be used, for example, for the synthesis of ethers for use as additives in automobile fuels or as a monomer for the synthesis of polyisobutene.